Insurers are slashing payments to medical practices in many of the plans they sell through the new health-law marketplaces—sparking worries that Americans signing up for coverage will have fewer doctors to choose from if low fees spark an exodus from the plans.

UnitedHealth Group Inc. sent some New York City physicians contract amendments as recently as this month setting rates well below what doctors normally see from private...

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Insurers Cut Doctors' Fees in New Health-Care Plans

Insurers are slashing payments to medical practices in many of the plans they sell through the new health-law marketplaces—sparking worries that Americans signing up for coverage will have fewer doctors to choose from. Christopher Weaver reports. Photo: Getty Images.